I have a 2004 4.7L Tundra. I have some issues with the Knock Sensors. I've tried all I could at home without pulling the engine apart. I think its time for the dealership to rip me off,I mean rip the intake manifold off and change the knock sensors or tell me what's wrong with the engine. Truck runs great until the CEO comes in. I've had the truck at the dealership in 09 for this problem and they changed 4 O2 sensors and 2 CATs.... Still have the knock sensor code.

So my question is... While they have the top of the engine apart, what else can I have them do... Gaskets, knock sensors/wires, and.... Truck has 140k and I hope for it to be my weekend toy for many more. Any suggestions of proventative maintenance to get the most out of the labor costs?
Thanks.

Did all them problem s start after timing belt change? My tundra had the amended problems it was a chewed up wire harness that wasn't put back after the timing belt was replaced gave o2 cat misfire and knock sensor codes now

I never mentioned that I had the timing belt changed... I did around 90k. Good point however I believe this started around 115k. I had a "low flow cat" code if I remember correctly. After the dealership changed the card and o2 sensors they told me there was a knock code in the history and they also noticed one of the knock sensor wires had been butt spliced so it may cause issues in the future. I am an electrician and cant for the life of me find where these wires go after they leave the sensors so for anyone to be able to cut,strip,crimp these wires is beyond me. Anyways, the CEL light came back on with a Knock sensor Bank 1 less than 3 miles after leaving dealership. I called and they popped me for another $150 to tell me its the knock sensor bank 1 and its zzz$ to fix. This is all in 2009 so I don't have any records of this.

Mine was crimped too never ran right afterwards the serpentine had rubbed mine but also heard intake could rub em or crush em or something . I would check the harness. If it is the knock sensor rock auto has em $80or a piece

I had the same codes too and they told me not to worry about the knock sensor code that it was probably false boy were they wrong

Thanks for the info! However I've been searching for any type of info as to how these wires r routed.IDE love to take an ohm reading or voltage reading but the harness is so taped up I can't see where it actually is. Is it just 2 wires in the harness plug? One for each KS? I tore the dash apart last week trying to check at the ECU but my meter leads aren't that tiny... And it was getting dark out. Also, the dealer told u not to worry? When my CEL is on due to knock sensor it feels like I'm driving a steam engine truck... Add fuel and wait for it to build up pressure. No power,no pickup,and 8mpg. I'm a handy guy so if I can find a bad wire IDE love to get in there and repair it myself. Thanks!

Let me know how it goes id like to know where to ohm it out too! The tape kinda deterred me too. Never did get a chance to take it apart before the wife totaled it. Yes your truck will act bad when that code comes on my truck did a chitty chitty. Bang bang before it just gave up and said it had enough and left me stranded on a highway in the middle of nowhere. Dealership didn't tell me not to worry some auto place did that was my first mistake was taking it there. Im doing my own timing belt this time. Yes two wires into each knock sensor I know somewhere on this site someone posted a pdf manual for the tundra that had the info you need I just can't find it anymore I will look again

Free .pdf copies of various Toyota (Tundras included) Factory Service Manuals (FSMs) are available from Toyota Tacoma/ 4Runner/ Tundra/ FJ Cruiser Factory Service Manual Page (http://www.ncttora.com/fsm/index.html)

Ok I’m reading all of this and trying to make sense of everything . Every so often I get a chuckle out of answers given by others.
Yes your truck will run with lack of power. You need to understand what a knock sensor is there for.
The knock sensor senses what is known as non-audible knock (or extreme knock) of the power cylinder. If it senses knock it retards timing. Once the knock is gone it goes back to normal timing. If it senses it again it will again reduce the timing. Normally the computer advances the timing and runs the engine just outside of knock, where it runs at its best performance. If knock occurs (or it senses knock) the timing retards, lowering the operating performance. There are many strategies as to how the manufacture sets up the operating parameters of the control system.
In your case, the engine is running in a default or possibility open circuit. Once the computer sees the trigger from the sensor it goes to default timing, which could be 6° to 8° or even 12°retarded timing, keeping the engine out of knock. This amount of default retard is set by Toyota. This trigger can come from several things, you are truly into knock (in this case you have engine issues), sensor is bad (could be but I don’t think so), Computer problem (normally you would get other codes, Or a broken wire/bad connector (I would be looking for this, problem is you need to pull the manifold). I had a 2000 and a mouse chewed threw the wire. I used a borescope and looked under the intake and found it. If you find crimping on the wires that means there was a problem with the wire(s) before. The dealers or whoever fixed it crimped on a new wire and connector. Best repair is to strip back and solder the wires together. Crimp connections will last for a while but wires corrode and become loose with vibration. Yes the connectors become brittle after time from the heat. So if you are removing the connector from the sensor take care.
Knock sensors normally on a car or truck don't go bad unless someone damages them. They are very robust little things. Tundra used two different styles of knock sensors. Early sensors (threaded into the head) were a single wire Piezo-electric devise and later they went to a two wire sensor (Sumitomo connector) attached with a bolt or stud. The later sensor is black in color and has the connector plugged into the side while the early connector is silver in color and plugs in from the top. These sensors are not interchangeable. Both are Denso brand sensors. Sensors are built for the manufacture under certain guidelines and testing to insure that the knock thresholds meet certain operating windows. Throwing in a Rock Auto sensor may not be the correct sensor to use. I would stay with a Toyota brand unless you can match yours with the correct Denso brand.
Early Piezo-electric sensors internal resistance is 560 ohms plus or minus 56K ohms. The later sensors internal resistance should be 200K ohms plus or minus 40%.
On the Gen-1 Tundra there will be one sensor on each bank about midpoint of the cylinder head. You cannot get to the wiring unless you pull the intake. The wire harness runs from the back of the engine to the front and the harness and wires are tight. I think Toyota should have given a little more slack in the harness, this could lead to wires breaking. If you change the sensor make sure the surface of the head is very clean, and use the proper torque. If incorrectly torqued the sensor doesn't read correctly.
It’s not a bad job pulling the intake manifold, just time consuming. Be prepared. I found using a digital camera the best thing there is for the do it yourself project. Take lots of pictures as you are taking it apart and you can always go back and look and them if there are questions. I purchased all the replacements gaskets prior to tearing anything apart. I started around 8:00 AM on a Saturday and was done around noon. Make sure if you pull the manifold to put rags in the intake holes to keep debris from falling into the intake.
Next you said that the dealer found/flagged a bad sensor back in 2009? So the truck has been running with retarded timing for 3 years? The efficiency of the engine is at its worst running at its default timing.
3 years running this way? You must be burning twice the gas you should be. My 2006 gets around 17 MPG and dropping it to 8.5 MPG has to be hard on the pocket book. Wow is all I can say. Well, anyway, I hope this helps.

Great explanation. I think you have a typo so just wanted to point it out to you for correction. At the end of the 1st paragraph, you said "Early Piezo-electric sensors internal resistance is 560 ohms plus or minus 56K ohms." Did you mean "... internal resistance is 56K ohms plus or minus 560 ohms"? As currently stated, it could result in a negative resistance value. My FSM (for 2002) indicates the (single wire) sensor is defective if continuity is measured between the wire terminal and the body of the sensor. That would indicate it operates as an open or short, like a switch.

Yes, I did make a typo its 560K ohms plus or minus 56k ohms. By the way the corect female connector for this sensor is a Yazaki P/N 7283-1015-10. These can be found on the internet cheaper than buying them from Toyota.

Thanks for all of the info. Mddubins, it seems that you have done this job before.I take apart machinery and put back together for a living so this shouldn't be a problem for me. First off,I need to drain coolant correct? What parts should i have on hand? The upper and lower gaskets... Any rtv/high temp sealants? Whether I find something or not I'm going to replace wires... Should I fork over the cash and change the sensors aswell? My main question is coolant though... Must that be drained? And engine oil... Not going to be any that high up right? I may start this weekend... If the bolts crack easily ill order the gaskets, etc. Thanks again.

It's been a few years since I pulled the intake manifold. I seem to remember draining the coolant as there was something attached to the manifold that has coolant running through it. It was easier to drain than try to block it off.
As for parts, look it over. You know you'll need intake gaskets. Can you see anything else that attaches to the manifold that may need a gasket or o-ring? If you can get you hands on a parts manual you can see the break down of what you might need. Mark all your vaccumm hoses or document them well. Take things off in large chunks if you can, it make it's easier going back together again.
I went to Toyota and told the parts guy what I was doing and he pulled everything I needed and a few extra things that I didn't need. I just returned them when I was done.
As for oil you will not need to drain it for doing this job, but I would change it when you are completed with the intake project. It's good practice to drain and replace the oil when opening the engine, but that's up to you.
Replacing the sensors is up to you. I my case I found a broken wire and knew what the problem was. If I had to go through all that work pulling the manifold and know knowing or finding the root cause of the problem I guess I would replace them to be on the safe side. You need to remember replaceing them may not solve your problem, it may be somewhere else. If you do replace them make sure you get them from Toyoya, and get the torque valve needed to install.
If you need anything else I can look under my 2006 hood (I replaced the 2000 with a 2006) and see what I had to do. If you repair machinery you should be able to do this.
Good Luck,